This study presents the results of cyclic unconfined compression tests of cement-treated soil specimens prepared in a laboratory. Unconfined compression tests, in which a monotonic loading is applied to a specimen, are also conducted to evaluate the mean and variation of the unconfined compressive strength qu of the prepared specimens. The cyclic loading tests provide the cyclic strength qcyc versus the number of cycles to failure nf plots, which is known as S-N curve. The ratio of qcyc to qu at prescribed cycles is evaluated on the basis of the S-N curve obtained as the sample regression line. Moreover the variance of linear regression is analyzed because there is a large scatter in the data on the S-N plots. The comparison of the variance of linear regression with that of qu indicates that the variability of specimen strength results mainly in the variability in the data on the S-N plots.